rQuadTo
Adds quad from last point towards vector (dx1, dy1), to vector (dx2, dy2). Quad control is last point plus vector (dx1, dy1). Quad end is last point plus vector (dx2, dy2).
Return
this builder for chaining
Parameters
dx1
offset from last point to quad control on x-axis
dy1
offset from last point to quad control on y-axis
dx2
offset from last point to quad end on x-axis
dy2
offset from last point to quad end on y-axis